Switching mechanism



Aug 11, 1942. J. E. o sTL'lNE 2,292,471

SWITCHING MECHANI SM Filed May 13, 1940 .MSL/lahm I 39 L68' 67 3 HQ-S@ HUM 342/23, (40 ,f' 45 Fig. 3 f5 14 liti.

' 23 lzzzflQ-f L25 @5J l ATTORNEYS.

Patented Aug. 11, 1942 SWITCHING MECHANISM John E. Ostline, Chicago, Ill.,

ciated Electric Laborato ries, Inc.,

assignor to Asso- Chicago, Ill.,

a corporation of Delaware Application May 13, 1940, Serial No. 334,886

7 Claims.

The present invention relates to switching mechanism and more particularly to electromagnetic switching mechanism of the relay type.

Electrical control systems and particularly automatic telephone systems conventionally comprise a large number of electromagnetic relays which are selectively operated to complete different control circuits and which are held in their operated positions for considerable periods of time in order to retain completed the control circuits. Ordinarily, each relay is operated when the Winding thereof is energized and is held in its operated position by retaining its winding energized.

While a control system of the type described is entirely satisfactory in operation, the large number of relays which are held operated constitute, as a whole, a considerable load upon the source of electric current supply in the system.

Accordingly, it is an object of the present invention to provide improved electromagnetic switching apparatus of the relay type including a plurality of unit relays, each of which is operated electrically and retained in its operated position mechanically Another object of the invention is to provide improved switching mechanism of the type described, which is of rugged and compact construction and which is reliable and positive in operation.

A further object of the invention is to provide in an electromagnetic device comprising a master magnet and a plurality of unit magnets, an improved interlocking arrangement between the armature of the master magnet and the armatures of the unit magnets for selectively controlling the positions of the armatures of the unit magnets.

In brief, the objects set forth above are in part realized in accordance with one feature of the invention by providing switching mechanism which comprises a master magnet having a master armature associated therewith, means responsive to the energization of the master magnet for moving the master armature from its restored position to its operated position, means responsive to the deenergization of the master magnet for moving the master armature from its operated position back to its restored position, a plurality of unit magnets having a plurality of unit armatures individually associated therewith, and a plurality of restraining devices individually associated with the unit armatures, each of the restraining devices having a normal position and an operated position. Further the switching mechanism comprises means responsive to the momentary energization of any one of the unit magnets for urging the associated one of the unit armatures to move from its restored position to its operated position, whereby the one unit armature is moved from its restored position to its operated position in the event movement thereof is not prevented, means controlled by the movement of any one of the unit armatures from its restored position to its operated position for operating the associated one of the restraining devices from its normal position to its operated position, whereby the one unit armature is restrained in its operated position, means including an interlocking arrangement between the master armature and each of the unit armatures for positively preventing movement of each of the unit armatures from its restored position to its operated position when the master armature occupies a predetermined one of its positions, a plurality of contact sets individually associated with the restraining devices, and means for operating each one of the Contact sets in accordance with the operation of the associated one of the restraining devices. More particularly, the interlocking arrangement is so constructed that it not only constitutes means for positively preventing movement of each one of the unit armatures from its restored position to its operated position when the master armature occupies a predetermined one of its positions, but it also constitutes means for moving each one of the unit armatures occupying its operated position against the associated one of the restraining devices back to its restored position when the master armature is moved from the other of its positions to its one position.

In accordance with another feature of the invention, the switching mechanism comprises a magnet having an armature associated therewith, a movable member having a contact portion and a restraining portion, a stationary member having a contact portion associated with the contact portion of the movable member, the restraining portion of the movable member being associated with the armature, means responsive to the momentary energization of the magnet for operating the armature, means controlled by the operation of the armature for operating the Inovable member, whereby the contact portion of the movable member is moved with respect to the contact portion of the stationary member and the restraining portion of the movable member is moved into engagement with the armature in order to restrain the armature operated, means for restoring the armature, and means controlled by the restoration of the armature for restoring the movable member, whereby the contact portion of the movable member is moved with respect to the contact portion of the stationary member and the restraining portion of the movable member is moved into disengagement with the armature.

In accordance with a further feature of the invention, the switching mechanism comprises a support including an upstanding longitudinally extending web and a laterally projecting longitudinally extending flange, a master magnet carried by the support, a longitudinally extending master armature carried by the support and associated with the master magnet, a plurality of unit magnets carried by the web and arranged in longitudinally spaced-apart side-by-side relationship, a plurality of unit armatures carried by the flange and arranged in longitudinally i spaced-apart side-by-side relationship and individually associated with the unit magnets, means including the master magnet for controlling the position of the master armature,

and means controlled jointly by the position of the master armature and each one of the unit magnets for controlling the position of the associated one of the unit armatures.

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing in which Figure 1 is a fragmentary plan view, partly broken away, of an electromagnetic switching mechanism of the relay type constructed and arranged in accordance with the present invention; Fig. 2 is a fragmentary front elevational view of the switching mechanism shown in Fig. 1; and Fig. 3 is an enlarged end elevational view of the switching mechanism and a diagrammatic illustration of certain control circuits associated therewith.

Referring now more particularly to Figs. l to 3, inclusive, of the drawing, the switching mechanism there shown comprises an elongated longitudinally extending support I having a substantially Z-shaped cross section including a laterally projecting body II, an upstanding web I2 and a laterally projecting flange I3. The body II carries a master magnet I4 comprising a field structure I5 carrying a winding spool I6 supporting a winding I1. More particularly, the field structure I5 is rigidly secured to a substantially L-shaped supporting bracket I8 by two collars I9, the bracket I8 being suitably fastened to the body II. Also the collars I9 securely retain the winding spool I6 in place upon the field structure I5.

Further, a substantially rectangular bracket surrounding the winding spool I6 is secured t0 the body II and carries a pivot pin 2| upon which a substantially T-shaped master armature 22 is pivotally mounted. More particularly, the master armature 22 comprises a stem 23 which carries a pair of lugs 24y pivotally mounted upon the pivot pin 2I and a head 25. The eld structure I5 of the master magnet I4 and the master armature 22 are so constructed and arranged that one leg of the field structure I5 is operatively associated with the stem 23 of the master armature 22 adjacent the outer end thereof and another leg of the eld structure I5 is operatively associated with the stem 23 of the master armature 22 adjacent the lugs 24 and consequently adjacent the pivot pin 2|; while the head 25 of the master armature 22 projects below the flange I3, for a purpose more fully explained hereinafter.

The web I2 carries a plurality of unit magnets 26 arranged in longitudinally spaced-apart sideby-side relationship, each unit magnet 26 carrying a winding spool 21 supporting a winding 2B. Also each unit magnet 26 is provided with a field structure including the adjacent portions of the web I2 and the flange I3. The flange I3 carries a longitudinally extending pivot pin 29 upon which there are supported a plurality of unit armatures 30 arranged in longitudinally spacedapart side-by-side relationship and individually associated with the unit magnets 26. More particularly, each unit armature 3D is substantially L-shaped comprising a body 3I carrying two spaced-apart lugs 32 pivotally mounted upon the pivot pin 29 and an arm 33 disposed below the flange I3. More particularly, the arm 33 of each unit armature 30 is disposed between the flange I3 and the outer end of the head 25 of the master armature 22, the arm 33 of each unit armature 30 carrying an insulating stop 34 adapted to engage the lower surface of the flange I3 and the head 25 of the master armature 22 carrying a plurality of longitudinally spaced-apart insulating stops 35 adapted to engage the lower surfaces of the arms 33 of the respective unit armatures 30. A resilient coil spring 36 is arranged between the web I2 and the head 25 of the master armature 22, one end of the coil spring 36 being secured to the head 25 and the other end of the coil spring 36 being secured to a tab 31 carried by the web I2. Accordingly, the coil spring 36 biases the master armature 22 in a counterclockwise direction about the pivot pin 2I, as viewed in Fig. 3, thereby to force the longitudinally spaced-apart stops 35 carried by the head 25 of the master armature 22 into engagements with the lower surfaces of the arms 33 of the various unit armatures 30 in order to cause the various unit armatures 30 to be rotated in a clockwise direction about the pivot pin 29, as viewed in Fig. 3, whereupon the longitudinally spaced-apart stops 34 carried by the arms 33 of the various unit armatures 30 are moved into engagements with the lower surface of the flange I3.

Further the switching mechanism comprises a longitudinally extending plate 38 having an upturned flange 39 on the outer end thereof, constituting a contact bar, and a plurality of longitudinally spaced-apart contact rods 40. The plate 38 and the contact rods 40 are secured to the body II by an arrangement `comprising a longitudinally extending clamping plate 4I., a plurality of longitudinally extending insulating strips 42 and a number of screws 43, the insulating strips 42 being arranged interbetween the body II, the plate 38, the contact rods andv the clamping plate 4I in order to` insulate each of these members from the other, and the screws 43 extending throughl aligned openings `provided in the clamping plate 4I and the insulating strips 42 and threaded into tapped holes formed in the body II. Also it is noted that the Contact bar 39 has a plurality of longitudinally spaced-apart notches 44 n the upper edge thereof, each one of these notches 44 ,being substantially V-shaped and disposed below an associated one ofY the contact rods 49, whereby each notch 44 is adapted to receive the associated contact rod and to make twin contact therewith. Preferably, the contact bar 39 and at least the contact portions of the contact rods 40 are plated with an arc-resistant material, such as silver, in order to minimize corrosion of these elements incident to operation of the switching mechanism. The outer end of each of the contact rods 40 is provided with a restraining portion which cooperates with a restraining portion 46 provided on the outer end of the body 3| of an associated one of the unit armatures 30. Preferably, the restraining portion 45 of each contact rod 4|) and the cooperating restraining portion 46 of the associated unit armature 39 each have a substantially V-shape and cooperate in a manner more fully described hereinafter.

Finally the switching mechanism comprises a set of switch springs 41 carried by the bracket 29 and operatively associated with the master armature 22. More particularly, the set of switch springs 4l includes three switch springs 48, 49 and 59 and is securely fastened to the bracket 20 by an arrangement comprising a clamping plate 5|, a number of insulating strips 52 `and a screw 53, the insulating strips 52 being arranged interbetween the bracket 20, the switch springs 48, 49 and 50 and the clamping plate 5| in order to insulate these elements from each other and J the screw 53 extending through aligned openings .provided in the clamping plate 5| and the insulating strips 52 and threaded into a tapped hole formed in the bracket 2|). The switch spring 48 is directly connected to the outer end of the head 25 of the master armature 22 by an insulating post 54 and is operatively associated with the switch spring 50, whereas the switch spring 59 is operatively associated with the switch spring 49.

Referring now more particularly to Fig. 3 of the drawing the various control and controlled circuits for the switching mechanisms are diagrammatically illustrated. An operating circuit for the master magnet I4 is provided which comprises a grounded battery 69, a control key KII, the winding i 'I of the master magnet I4, the switch spring 5U and the grounded switch spring 49; and a holding circuit for the master magnet I4 is provided which comprises the grounded battery 54, the control key KGI, the winding I7 of the master magnet I4, the switch spring 59, the switch spring 48 and the grounded resistor 62. An operating circuit for one of the unit magnets 26 is provided which comprises a grounded battery 63, the wiper 64 and the second contacts 65 of a rotary switch S66 and the grounded winding 28 of the unit magnet 26. A circuit controlled jointly by the master magnet I4 and one of the unit magnets 26 is provided which cornprises a grounded battery 61, a load lamp L68, one of the :contact rods 49 and the grounded yplate 33.

In View of the foregoing description of the construction and arrangement of the switching device, it will be understood that when the winding Il of the master magnet I4 is deenergized the master armature 22 is biased in a counterclockwise direction about the pivot pin 2|, as viewed in Fig. 3, 'by the coil spring 36, thereby to cause the head 25 of the master armature 22 to bias each of the unit armatures 39 in a clockwise direction about the pivot pin 29, as viewed in Fig. 3. When each of the unit armatures 3U is rotated in the clockwise direction about the pivot -pin 29,

the restraining portion 46 provided on the outer end of the body 3| thereof cooperates with the restraining portion 45 provided on the outer end of the associated contact rod 46, thereby to force the outer end of the associated contact rod 40 upwardly away from the cooperating notch 44 provided in the contact bar 39 carried by the plate 38, whereupon the previously traced circuit for energizing the associated load lamp L68 is retained interrupted.

In order to render the switching device operative, the previously traced operating circuit for energizing the winding I'I of the master magnet I4 is first completed by actuating the control key K6I. When the operating circuit for energizing the winding I'I of the master magnet I4 is completed, a magnetic flux is set up in the field structure I5 of the master magnet I4 which traverses the stem 23 of the master armature 22 in an obvious manner, thereby to cause the master armature 22 to be rotated in a clockwise direction about the pivot pin 2 I, as viewed in Fig. 3. When the master armature 22 is rotated in a clockwise direction about the pivot pin 2|, the switch springs 48 and 5t are rst operated into engagement due to the connection of the switch spring 48 to the head 25 of the master armature 22 by the insulating post 54, and then the switch springs 49 and 59 are operated into disengagement. Accordingly, upon operation of the master armature 22, the previously traced holding circuit for energizing the winding I1 of the master magnet I4 is first completed and then the operating circuit for energizing the winding II of the master magnet I4 is interrupted, the master armature 22 being retained in its operated position so long as the holding circuit for energizing the winding I'I of the master magnet I4 is completed. It is noted that the holding circuit for energizing the winding I'I of the master magnet I4 includes the resistor t2, thereby to reduce the holding current flowing in this holding circuit after the master armature 22 has been operated.

When the master armature 22 is rotated in a clockwise direction about the pivot pin 2|, the head 25 thereof is moved away from the flange I3, thereby to cause the stops 35 to disengage the lower surfaces of the arms 33 of the associated unit armatures 3|), whereupon each of the unit armatures 36 is rendered free to rotate in a counterclockwise direction about the pivot pin 29, as viewed in Fig. 3. In order to operate one of the unit armatures 33, the winding 28 of the associated one of the unit magnets 25 is momentarily energized by operating the rotary switch S66. In order to energize the winding 2S of the unit magnet 26 illustrated, the rotary switch S66 is operated in order to cause the wiper 64 thereof to engage momentarily the second Contact thereof, thereby momentarily to complete the previously traced circuit for enel'- gizing the winding 28 of the unit magnet 26. When the winding 26 of the unit magnet is thus momentarily energized a magnetic flux is set up in the associated eld structure including the adjacent portions of the web I2 and the flange I3 in an obvious manner, thereby to cause the unit armature 39 to be rotated in a counterclockwise direction about the pivot pin 29, as viewed in Fig. 3. When the armature 3d is rotated in a counterclockwise direction about the pivot pin 29, the restraining portion 46 provided on the outer end of the body 3i thereof cooperates with the restraining portion 45 provided on the outer end of the associated contact rod 40 in order to cause the associated contact rod 40 to be movedv downwardly into engagement with the associated notch iti-4 provided in the contact bar 39, whereupon the previously traced circuit for energizing the load lamp L58 is completed. More particularly, the restraining portion 46 carried on the outer end of the body 3| of the unit armature 30 rides under the restraining portion 45 carried on the outer end of the associated contact rod 40 in order to cause these two restraining portions to be retained in interlocking relationship, whereby the unit armature 30 is restrained against movement in a clockwise direction about the pivot pin 29, as viewed in Fig. 3. Accordingly, when the circuit for energizing the winding 28 of the unit magnet 2t is subsequently interrupted, the associated unit armature 30 is restrained in its operated position due to the cooperation between the restraining portion 45 provided on the outer end of the body 3| of the unit armature 39 and the restraining portion 45 provided on the outer end of the associated contact rod 40.

Thus it will be understood that any number of the unit armatures 39 may be operated by causing the windings 28 of the associated unit magnets 26 to be energized momentarily, each of the unit armatures being restrained in its operated position incident to operation thereof. Also as each unit armature is operated and restrained in its operated position by the associated contact rod 40, the circuit for energizing the associated load lamp L63 is completed.

In view of the foregoing description of the mode of operation of the switching apparatus, it

`will be understood that the arrangement whereby the unit armatures are selectively operated electrically and restrained in their operated positions mechanically considerably reduces the load upon the source of electric current supply in the control system as only the winding I1 of the master magnet I4 is retained energized, regardless of the number of unit armatures which are restrained operated.

In order to restore the switching apparatus to its normal position, it is only necessary to actuate the control key KBI in order to interrupt the holding circuit for energizing the winding I1 of the master magnet I4, thereby to cause the master armature 22 to be rotated in a counterclockwise direction about the pivot pin 2 I, as viewed in Fig. 3, by the coil spring 35. When the master armature 22 is rotated in a counterclockwise direction about the pivot pin 2 Iy the switch springs 49 and 50 are actuated back into engagement and subsequently the switch springs 4B and 50 are actuated into disengagement in an obvious manner. Further, when the master armature 22 is rotated in a counterclockwise direction about the pivot pin 2|, the head 25 thereof is moved toward the ange I3, thereby to cause the stops 35 to engage the lower surfaces of the arms 33 of the associated unit armatures 30, whereupon each operated one of the unit armatures 30 is rotated in a clockwise direction about the pivot pin 29, as viewed in Fig. 3, back to its restored position. When each unit armature 30 is rotated in a clockwise direction about the pivot pin 29, the stop 34 carried by the arm 33 thereof engages the lower surface of the flange I3 in order to limit the movement thereof, and the restraining portion 46 provided on the outer end of the body 3| of the unit armature 30 rides from under the restraining portion 45 provided on the outer end of the associated contact rod 40 in order to cause the associated contact rod 40 to be moved upwardly and out of engagement with the associated notch 44 provided in the contact bar 39. When the contact rod 40 is moved out of the associated notch 44 in the contact bar 39, the circuit for energizing the associated load lamp L68 is interrupted in an obvious manner.

In view of the foregoing description of the mode of operation of the switching apparatus, it will be understood that each of the unit armatures 30 is retained in its restored position while the master armature 22 occupies its restored position due to the interlock therebetween; that each of the unit armatures 30 is rendered operative from its restored position to its operated position only when the master armature 22 occupies its operated position due to the interlock therebetween; that while the master armature 22 occupies its operated position each one of the unit armatures 30 may be operated from its restored position to its operated position by momentarily energizing the winding 28 of the associated one of the unit magnets 26; and that while the master armature 22 occupies its operated position each of the unit armatures 30 is restrained in its operated position after it is operated by the restraining arrangement associated therewith. Finally it is noted that when the winding I1 of the master magnet I4 is deenergized, the master armature 22 is returned to its restored position, thereby to cause each operated one of the unit armatures 3|) to be returned to its restored position.

In view of the foregoing it is apparent that improved electromagnetic switching mechanism of therelay type is provided which is of rugged and compact construction and which is reliable and positive in operation.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. Switching mechanism comprising a master magnet having a master armature associated therewith, said master armature being moved from its restored position to its operated position 1n response to the energization of said master magnet and being moved from its operated position back to its restored position in response to the deenergization of said master magnet, a plurality of unit magnets having a plurality of unit armatures individually associated therewith, a plurality of restraining devices individually associated with said unit armaturesq each of said restraining devices having a normal position and an operated position, any one of said unit armatures being urged to move from its restored position to its operated position in response to the momentary energization of the associated one of said unit magnets, whereby said one unit armature is moved from its restored position to its operated position in the event movement thereof is not prevented, means controlled by the movement of any one of said unit armatures from its restored position to its operated position for operating the associated one of said restraining devices from its normal position to its operated position, whereby said one unit armature is restrained in its operated position, means including an interlocking arrangement between said master armature and each of said unit armatures for positively preventing movement of each of said unit armatures from its restored position to its operated position when said master armature occupies a predetermined one of its positions, a plurality of contact sets individually associated with said restraining devices, and means for operating' each one of said Contact sets in accordance with the operation of the associated one of said restraining devices.

2. Switching mechanism comprising a master magnet having a master armature associated therewith, said master armature being moved from its restored position to its operated position in response to the energization of said master magnet and being moved from its operated position back to its restored position in response to the deenergization of said master magnet, a plurality of unit magnets having a plurality of unit armatures individually associated therewith, a plurality of restraining devices individually associated with said unit armatures, each of said restraining devices having a normal position and an operated position, any one of said unit armatures being urged to move from its restored position to its operated position in response to the momentary energization of the associated one oi said unit magnets, whereby said one unit armature is moved from its restored position to its operated position in the event movement thereof is not prevented, means controlled by the movement of any one of said unit armatures from its restored position to its operated position for operating the associated one of said restraining devices from its normal position to its operated position, whereby said one unit armature is restrained in its operated position, means including an interlocking arrangement between said master armature and each of said unit armatures for positively preventing movement of each of said unit armatures from its restored position to its operated position when said master armature occupies a predetermined one of its positions and for moving each one of said unit armatures occupying its operated position against the associated one of said restraining devices back to its restored position when said master armature is moved from the other of its positions to its one position, a plurality of contact sets individually associated with said restraining devices, and means for operating each one of said contact sets in accordance with the operation of the associated one of said restraining devices.

3. Switching mechanism comprising a master magnet having a master armature associated therewith, said master armature being moved from its restored position to its operated position in response to the energization of said master magnet and being moved from its operated position back to its restored position in response to the deenergization of said master magnet, a plurality of unit magnets having a plurality of unit armatures individually associated therewith, a plurality of restraining devices individually associated with said unit armatures, each of said restraining devices having a normal position and an operated position, any one of said unit armatures being urged tomove from its restored position to its operated position in response to the momentary energization of the associated one of said unit magnets, whereby said one unit armature is moved from its restored position to its operated position in the event movement thereof is not prevented, means controlled by the movement of any one of said unit armatures from its restored position to its operated position for operating the associated one of said restraining devices from its normal position to its operated position, whereby said one unit armature is restrained in its operated position, means including an interlocking arrangement between said master armature and each of said unit armatures for positively preventing movement of each of said unit armatures from its restored position to its operated position when said master armature occupies a predetermined one of its positions, a plurality of contacts individually carried by said restraining devices, and a contact bar commonly associated with said contacts, each one of said contacts being moved into engagement and disengagement with said contact bar in accordance with the operation of the associated one of said restraining devices.

4. Switching mechanism comprising a magnet having an armature associated therewith, a restraining device associated with said armature, said armature being operated in response to the momentary energization of said magnet, means controlled by the operation of said armature for operating said restraining device into restraining engagement with said armature, whereby said armature is restrained operated, means for positively restoring said armature against the restraining engagement of said restraining device, said restraining -device being restored in response to restoration of said armature, and a contact set controlled by said restraining device.

5. Switching mechanism comprising a magnet having an armature associated therewith, a movable Contact, said armature being operated in response to the momentary energization of said magnet, means controlled by the operation of said armature for operating said movable contact into restraining engagement with said armature, whereby said armature is restrained operated, means for positively restoring said armature against the restraining engagement of said movable contact, said movable contact being restored in response to restoration of said armature, and a stationary contact operatively associated with said movable contact.

6. Switching mechanism comprising a magnet having an armature associated therewith, a movable member having a contact portion and a restraining portion, a stationary member having a contact portion associated with the contact portion of said movable member, the restraining portion of said movable member being associated with said armature, said armature being operated in response to the momentary energization of said magnet, means controlled by the operation of said armature for operating said movable member, whereby the contact portion of said movable member is moved with respect to the contact portion of said stationary member and the restraining portion of said movable member is moved into restraining engagement with said armature in order to restrain said armature operated, and means for positively restoring said armature against the restraining engagement of the restraining portion of said movable member, said movable member being restored in response to restoration of said armature,whereby the contact portion of said movable member is moved with respect to the contact portion of said stationary member and the restraining portion of said movable member is moved out of restraining engagement with said armature.

7. A unitary electromagnetic device comprising a longitudinally extending support, a master magnet carried by said support, a longitudinally extending master armature carried by said support and associated with said master magnet, said master armature being operated in response to the energization of said master magnet and being restored in response to the deenergization of said master magnet, a plurality of longitudinally spaced-apart unit magnets carried by said support, a plurality of longitudinally spacedapart unit armatures carried by said support and individually associated with said unit magnets, any one of said unit armatures being urged to operate in response to the energization of the associated one of said unit magnets, whereby said one unit armature is operated in the event it is not prevented from operating, a plurality of restraining devices carried by said support and individually associated with said unit armatures, each of said restraining devices being adapted mechanically to restrain operated the associated unit armature in response to operation thereof, and means including an interlocking arrangement between said master armature and each of said unit armatures for positively preventing operation of each of unit armatures while said l0 master armature is restored and for restoring each operated one of said unit armatures against its associated restraining device in response to restoration of said master armature.

JOHN E. OSTLINE. 

